1. Field of the Invention
The present invention relates to a titanium alloy of low Young's modulus, which provides high strength, low elasticity modulus, and high elastic deformability.
2. Description of the Related Art
As having advantages of specific strength and corrosion resistance, titanium alloys are in general use for various specific fields of arts, such as aviation, defence, aerospace, deepwater exploration, and chemical industry.
Microstructures of titanium alloys may have polymorphism dependent on both temperature and chemical composition. An α phase and a β phase are representatives of thermodynamically stable phases composing microstructures of titanium alloys, and are respectively correspondent to a stable phase at the room temperature and a high-temperature phase of pure titanium. A temperature at which transformation between the α phase and the β phase occurs is referred to as a beta transus temperature. Some additive elements such as vanadium lower the beta transus temperature. Upon adding proper amounts of such elements, the beta transus temperature may be lowered close to or even under the room temperature, and therefore some titanium alloys has microstructures including a β phase at the room temperature. More specifically, some titanium alloys could be classified into an α type, an α+β type, and a β type, based on phases included in these microstructures.
As well as the above thermodynamically stable phases of the α phase and the β phase, martensite phases may also appear in titanium alloys. Martensite is a general name for any distorted microstructures resulted from transformation without atomic diffusion, and, in a case of titanium alloys, may typically appear when any of the titanium alloys is quenched from temperatures over the beta transus temperature.
A Ti-6% Al-4% V alloy classified as the α+β type is widely used for the reason of its high strength. As β type titanium alloys used hitherto, Ti-15V-3Cr-3Sn-3Al and Ti-22V-4Al alloys are known and applied to spectacle frames, golf clubs and such, as having flexibility.
Regarding Young's moduli of the titanium alloys used hitherto, it should be noted that those of the α type alloys are on the order of 115 GPa, those of the α+β type alloys such as the Ti-6Al-4V alloy are on the order of 110 GPa, and those of the β type alloys are on the order of 80 GPa after solution treatments, and on the order of 110 GPa after aging treatments.